1. Field of the Invention
The present invention relates primarily to a laminated aperture antenna suitable to communications using high-frequency waves such as microwave and millimeter wave and to a multi-layered wiring board comprising such a laminated aperture antenna.
2. Description of the Related Art
Studies on mobile communications, inter-vehicular radars or the like using high-frequency waves such as microwave and millimeter wave are actively conducted lately in the technological field of telecommunication. Normally, input/output of high-frequency signals between equipments in such communication is conducted by means of antenna in the end. While various antennas for the use of high-frequency waves have been examined since the past, a slotted waveguide antenna, a microstrip antenna, an aperture antenna and the like have been known as typical ones.
Further, while these high-frequency antennas are used by being connected with a high-frequency electrical circuit, a waveguide is used for the aperture antenna and the slotted waveguide antenna and a triplate line is used mainly for the microstrip antenna as a feed line connecting the electrical circuit and the antenna.
A planar array antenna in which a plurality of radiating elements formed of a hole whose inner face is metallized are disposed and are connected each other by a waveguide having a hollow section has been also proposed in Japanese Unexamined Patent Publication JP-A-62-222702.
It is also desired, recently, to integrate the antenna with a package in which a high-frequency circuit and high-frequency elements are stored from the aspect of miniaturizing the communication system equipment including the high-frequency antenna.
The antenna itself must be light, thin and small in order to use the high-frequency antenna as described above for the mobile communications, the collision avoidance radars and the like.
Among the high-frequency antennas described above, while the slotted waveguide antenna has advantages that it is highly efficient and that it can be formed thin, it also has disadvantages that it cannot be applied to a wide band, that it is heavy because it is fabricated by working a metal sheet and that it is costly. In contrary to that, while the microstrip antenna has advantages that it is light and can be formed thin because it is fabricated by adhering a metallic film on a dielectric sheet and that it is less costly because it can be fabricated readily, it has disadvantages that its efficiency is low and that it cannot be used in a wide band.
Meanwhile, the aperture antenna, e.g. a horn antenna, has advantages that it can be applied to a wide band and that its performance is very excellent in terms of the antenna characteristics, it has disadvantages that its size is large, that it is difficult to mount on a communication terminal and that it is difficult to lighten because it is fabricated by working three-dimensionally by using metallic members.
While the planar array antenna as disclosed in JP-A-62-222702 has advantages that it is light because it uses plastics as a base member thereof and it can be applied to a wide band, it has disadvantages that its feed section is thick and that it is difficult to miniaturize and thin it because the waveguide is used for the feed line.
When the high-frequency wave to be applied falls in the domain of millimeter wave, the characteristic of the whole antenna system becomes important in case when either one of the above-mentioned high-frequency antenna is used. That is, because the whole system is constructed by connecting the high-frequency antenna, the feed line, the high-frequency circuit and others in the end, the whole antenna system is influenced also by the characteristic, size, cost and others of the part connecting them no matter how their individual characteristic is excellent. For example, when the connecting part thereof is constructed by waveguides, the antenna system may be constructed almost without impairing the performance of the high-frequency antenna, the feed line, the high-frequency circuit and the like. However, there arise problems when they are connected by the waveguide that its structure is liable to be three-dimensional and that it drops the reliability and increases the cost because they are connected mechanically by screws and the like.
While the planar array antenna disclosed in JP-A-62-222702 excels as an antenna itself in this aspect because the antenna section is molded in a body with the feed line, it has had problems that its connectivity with other components such as the high-frequency circuit is bad and that it is difficult to form them in a body.